1362250-82-5Relevant academic research and scientific papers
Facing unexpected reactivity paths with ZrIV-pyridylamido polymerization catalysts
Luconi, Lapo,Rossin, Andrea,Tuci, Giulia,Tritto, Incoronata,Boggioni, Laura,Klosin, Jerzy J.,Theriault, Curt N.,Giambastiani, Giuliano
, p. 671 - 687 (2012)
This work provides original insights to the better understanding of the complex structure-activity relationship of ZrIV-pyridylamido-based olefin polymerization catalysts and highlights the importance of the metal-precursor choice (Zr(NMe2)4 vs. Zr(Bn)4) to prepare precatalysts of unambiguous identity. A temperature-controlled and reversible σ-bond metathesis/protonolysis reaction is found to take place on the ZrIV-amido complexes in the 298-383 K temperature range, changing the metal coordination sphere dramatically (from a five-coordinated tris-amido species stabilized by bidentate monoanionic {N,N-} ligands to a six-coordinated bis-amido-mono-amino complexes featured by tridentate dianionic {N-,N,C-} ligands). Well-defined neutral Zr IV-pyridylamido complexes have been prepared from Zr(Bn)4 as metal source. Their cationic derivatives [ZrIV{N -,N,C-}Bn]+[B(C6F5) 4]- have been successfully applied to the room-temperature polymerization of 1-hexene with productivities up to one order of magnitude higher than those reported for the related HfIV state-of-the-art systems. Most importantly, a linear increase of the poly(1-hexene) Mn values (30-250 kg mol-1) has been observed upon catalyst aging. According to that, the major active species (responsible for the increased Mn polymer values) in the aged catalyst solution, has been identified. Copyright
